Update app

[md8n]

A fairly hefty PR

The focus is on reducing the size of app.js

But that includes:

• index.html - some consolidation of embedded script, additional script inclusions, special reordering of script inclusions.
• connectdlg.js - some minor cleanup
• grbl.js - moving the onReportType event handler function out to
• grblpanel.js - a new js file to handle the enormous volume of event handlers in the grbl panel
• grblpanel.html - removal of every on* attribute in the html, replaced with ids and the above event handlers
• socket.js - a new js file for a lot of the socket handling code that was in app.js, and one that was in http.js
• http.js - moved out a function from here that wasn't a good fit.
• util.js - moved one small function to here.
• preferencesdlg.js - moved the ontogglePing function to here, where it is used.
• navbar.html and navbar.js - similar to what was done for the grblpanel

and finally app.js - with a massive clean out so that it is focussed on app startup and not much else.

[BarbourSmith]

These are great changes in theory, but I'm still not able to control the machine anymore with error messages:

Uncaught ReferenceError: can't access lexical declaration 'id' before initialization
    loadJogDists http://maslow.local/:63
    <anonymous> http://maslow.local/:63
[maslow.local:63:44039](http://maslow.local/)
Uncaught ReferenceError: can't access lexical declaration 'displayNone' before initialization
    onload http://maslow.local/:57